I. Field of the Invention
This invention relates generally catheter structures adapted to be introduced into a living body, and more specifically to the design of a catheter which may be introduced and routed through the vascular system of a patient with a minimum of damage or trauma to endothelial tissue.
II. Discussion of the Prior Art
Present day surgical procedures permit the introduction of tubular catheters into the vascular system of a body. For example, angiographic catheters are commonly introduced into the femoral artery and routed through the arterial system and to the coronary ostium so that radiopaque contrast or medicaments may be injected as part of a diagnostic or treatment procedure. Typically, such catheters comprise elongated, flexible plastic tubes of a predetermined small diameter significantly less than the cross section of the vessels through which the catheter must pass. Other forms of catheters which the present invention may find use are those associated with cardiac pacemakers. Here, the catheter takes the form of a pacing lead which is typically made to pass through the subclavian vein and through the superior vena cava into the right ventrical of the heart. Here, the catheter takes the form of a flexible sheath surrounding elongated conductors which terminate at the distal end in one or more surface electrodes adapted to contact endocardial heart tissue.
Prior art, angiographic and other diagnostic catheters as well as cardiac pacing leads are generally formed from polyethylene, polyurethane, polypropylene or silicone rubber or other non-thrombogenic material. So that they may be passed through the vascular system without folding or buckling, they must possess a wall thickness and a hardness which is capable of damaging vascular tissue, especially where the distal tip of the catheter is blunt or possessed of a sharp edge. While perhaps rare, there have been instances where small diameter catheters having sharp edged tips have been advanced through the wall of the aorta, resulting in the death of the patient.